1. Field of the Invention
The present invention generally relates to image sensing modules for optical imaging devices and more particularly relates to image sensing modules practically suitable for being integrated into portable computing devices, wherein the portable computing devices may include, but not be limited to, a palm pilot, a mobile phone and a personal data assistant (PDA).
2. Description of the Related Art
There are many applications that need optical imaging devices to convert paper-based objects, such as texts and graphics, to an electronic format that can be subsequently analyzed, distributed and archived. One of the most popular optical imaging devices are flatbed scanners that typically convert scanning objects, including pictures and papers, to images that can be used for example, for building world wide web pages and optical character recognition. Another emerging optical imaging device is what is called sheet-fed scanners that are small and unobtrusive enough to sit between a keyboard and a computer monitor or integrated into a keyboard to provide a handy scanning means. Most optical scanners are referred to as image scanners as the output thereof is generally in digital format.
FIG. 1 illustrates a cross section of an exemplary image sensing module 100 that is typically used in those image scanners. Image sensing module 100 includes a light source 102, an optical system 108, and an image sensor 110, all are cast in an elongated rectangular tube. When scanning object 120 passes through image sensing module 100, it is illuminated by light source 102 through a window 116. The light reflected by scanning object 120 is then focused through optical path 114 by optical lens system 108 onto image sensor 110. An image of scanning object 120 is therefor generated.
Portable imaging devices containing image sensing module 100 have been used as PC scanners, facsimiles and other multi-function peripherals. However, with the recent explosion of the mobile personal computing market, the demand for effective, mobile internet-connective digital imaging and scanning is increasing at a tremendous rate. Optical imaging devices smaller than the existing sheet-fed type scanners are required in many applications, for example, as an integral part of a palm pilot. An image sensing module is a key component in portable imaging devices. Its dimension is vital to the overall size of the entire imaging device. As shown in FIG. 1, in image sensing module 100, scanning object 120 is perpendicular to optical system 108. With required length of optical path 114, it would be impractical to use an image sensing module as shown in FIG. 1 in a portable imaging device. There is therefore a need for smaller designs of an image sensing module practically suitable for being integrated in portable imaging devices.
The present invention has been made in consideration of the above described challenge and needs and has particular applications to portable computing devices that may include, but not be limited to, a palm pilot, a mobile phone and a personal data assistant (PDA).
According to one aspect of the present invention, distinct designs are provided to reduce dimensions of an image sensing module without affecting the sizes of the original individual components in the image sensing module. According to one embodiment, a mirror is mounted before an optical focus system and used to collect and redirect reflected light from a scanning object being illuminated by an illumination source in the image sensing module. In this configuration, the scanning object can be placed parallel to the optical lens system. The resultant image sensing module is much slimmer compared to the existing image sensing module.
According to another embodiment of the present invention, the image sensing module comprises an elongated rectangular case or tube. The components, such as an image sensor, an illumination source and an optical lens system, are placed at an angle in the elongated rectangular case such that the size of the elongated rectangular case is minimized without affecting the size of the components. The new configuration results in an image sensing module of reduced size and particularly suitable for the portable computing devices equipped with image scanning capability.
Accordingly, an important object of the present invention is to provide generic solutions for an image sensing module of reduced size.
Other objects, together with the foregoing are attained in the exercise of the invention in the following description and resulting in the accompanying drawings.